Réponse:
a.
phrase 1 :
verbe : was
phrase 2 :
verbe : was, was
phrase 3 :
verbe : was
phrase 4 :
verbe :was
phrase 5 :
verbe : were ,was
phrase 6 :
verbe : were
L'infinitif est "be".
IL est conjugué au prétérit et au singulier , au pluriel.
b.
phrase 1 : in 2018
phrase 2 : at school
phrase 3 : in history
phrase 4 : a few months ago
phrase 5 : ???
phrase 6 : Yesterday
c.
there was : IL y avait +singulier
there were : IL y avait +pluriel
there was est suivi du singulier dans une phrase
ex : there was a dog.
there were est suivi du pluriel dans une phrase
ex : there were dogs.
there was a dog and a cat.